title: Increased pathogenicity of an Ehrlichia-like agent after passage through Amblyomma hebraeum: a preliminary report.
abstract: After being passaged through 3 generations of Amblyomma hebraeum, an Ehrlichia-like agent isolated from an adult Hyalomma truncatum female became more pathogenic and elicited a disease in sheep indistinguishable from heartwater. Cross-immunity between this agent and several stocks of Cowdria ruminantium and high levels of antibody elicited by the agent against 2 stocks of C. ruminantium in the indirect fluorescent antibody test, confirmed its close relationship to Cowdria.
authors.affiliation: Veterinary Research Institute, Onderstepoort.
authors.forename: J L
authors.initials: JL
authors.lastname: du Plessis
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000209:etiology*; D003429:Cross Reactions; D004536:Ehrlichia / Q000276:immunology / Q000472:pathogenicity*; D012281:Rickettsia / Q000276:immunology; D012288:Rickettsiaceae Infections / Q000209:etiology / Q000662:veterinary*; D012692:Serial Passage; D012756:Sheep; D012757:Sheep Diseases / Q000209:etiology*; D013987:Ticks / Q000382:microbiology*